l. Field of the Invention
This invention relates to a self-cleaning plate shaped device which, for example, can be utilized for an automotive rear-view mirror.
2. Description of the Related Art
Japanese Laid-Open patent publication No. 59-8548 published on Jan. 17, 1984 discloses a conventional cleaning device of an automotive rear-view mirror. Referring now to FIG. 10, the conventional device comprises a plate member 1 of the automotive mirror, a vibrator 2 for vibrating the plate member 1, and an oscillator 3 for supplying A.C. power to the vibrator 2. Water drops on the plate member 1 are removed by vibration of the plate member 1 The water droplets on the plate member 1 drop off and are atomized away when the plate member 1 is vibrated.
The entire plate member 1 must be vibrated uniformly in order to remove water drops from the whole surface of the plate member 1. The conventional device utilizes a vibrator 2 which has substantially the same dimensions as the plate member 1 in order to vibrate the whole surface of the plate member 1.
However, localized oscillations may be generated in part of the vibrator 2 due to the influence of the principal vibration of the plate member 1, if the vibrator 2 has substantially the same dimension as the plate member 1. These localized oscillations may concentrate stresses into pinpoint locations which may generate heat. The concentrated stresses may generate cracks in the vibrator 2 and the generated heat may represent waste heat. Thus, the durability of the vibrator 2 may deteriorate and the amount of wasted power may increase.